css/css-cascade/scope-shadow.html

<!DOCTYPE html>
<title>@scope - ShadowDOM</title>
<link rel="help" href="https://drafts.csswg.org/css-cascade-6/#scope-atrule">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/declarative-shadow-dom-polyfill.js"></script>

<div id=host_plain>
  <template shadowrootmode=open>
    <style>
      @scope (:host) {
        .a {
          z-index: 1;
        }
      }
    </style>
    <div class=a>
    </div>
  </template>
</div>
<script>
  setup(() => {
    polyfill_declarative_shadow_dom(document);
  });

  test(() => {
    let a = host_plain.shadowRoot.querySelector('.a');
    assert_equals(getComputedStyle(a).zIndex, '1');
  }, '@scope can match :host');
</script>

<div id=host_functional>
  <template shadowrootmode=open>
    <style>
      @scope (:host(div)) {
        .a {
          z-index: 1;
        }
      }
      /* Should not match: */
      @scope (:host(span)) {
        .a {
          z-index: 42;
        }
      }
    </style>
    <div class=a>
    </div>
  </template>
</div>
<script>
  setup(() => {
    polyfill_declarative_shadow_dom(document);
  });

  test(() => {
    let a = host_functional.shadowRoot.querySelector('.a');
    assert_equals(getComputedStyle(a).zIndex, '1');
  }, '@scope can match :host(...)');
</script>